In recent years, polycarbonate resin that is produced from 2,2-bis(4-hydroxyphenyl)propane (or, bisphenol A), because of having a high transparency and excellent mechanical properties, has been used in various applications including optical materials and electronic materials. One application among these is an electrophotographic photoreceptor.
Unit processes including corona charging or contact charging using rolls or brushes, toner development, image transferring to paper, and cleaning treatment are repeated on the surface of a photoreceptor of the electrophotographic photoreceptor, whereby electrical and mechanical external stresses are applied to the electrophotographic receptor on every occasion of the unit processes. Therefore, in order to maintain image quality over a long time, the photoreceptor layer that is disposed on the surface of the electrophotographic photoreceptor is required to have durabilities against the electrical and mechanical external stresses. Specifically, durabilities against development of wear or scar on the surface of the photoreceptor caused by friction and surface degradation caused by discharging or active gases such as ozone in the course of corona charging or contact charging and image transferring.
In order to meet these requests, polycarbonate resin, which has good optical properties and good compatibility with charge transporting materials used in the photoreceptor layer, has been used as a binder resin for the electrophotographic photoreceptor. However, conventional polycarbonate resin that is produced from the aforementioned bisphenol A, 1,1-bis(4-hydroxyphenyl)cyclohexane (or, bisphenol Z), and the like is not sufficient to satisfy the above requests, particularly abrasion resistance or the like.
Under the above circumstances, as a method of addressing the above problems, polycarbonate resins or polyester resins that have various molecular structures have been proposed. Furthermore, an attempt of improving the durabilities and electrophotographic properties by mixing these resins has been also reported. (Patent Documents 1 to 7). Patent Documents 1 to 6 include a report of informing that abrasion resistance is improved by mixing a specific polyester resin with a polyester resin or polycarbonate resin that has a different structure. Patent Document 7 discloses a binder resin that is a blend of a specific copolymerized polycarbonate resin and a polycarbonate resin that is obtained by using bisphenol Z solely as a dihydric phenol.